When a distributed electromagnetic instrument works, a transmitter generally transmits signals out, and transmits different frequency signals in different time periods in accordance with an established time parameter table. A plurality of receivers also set corresponding parameters in accordance with the same time parameter table, acquire the signals, and process and analyze the acquired signals. In general, the areas of operations where the transmitter and the receivers are located are at a distance of more than a few kilometers, the receivers are distributed in various places in accordance with a certain plan as well, without cables for connection and information interaction therebetween.
In order to synchronize the transmitter and the receivers in terms of actions, a method used currently is to configure GPS receivers on both the transmitter and the receivers, and perform a synchronization operation in accordance with GPS timing. Such a method has disadvantages that the time table used by the transmitter and receivers may be set only before the operation and may not be changed or adjusted once the operation has been started. However, in an actual field operation, measurement time required by different frequency signals is not identical due to different in-situ geologic characteristics of a work area. In order to obtain complete and high-quality data, it is necessary to set time of each frequency signal to be long enough when the time table is designed, and a current operation may be only stopped if parameters are changed or adjusted, which is not conducive to achieving high-efficiency operations.
Moreover, distributed electromagnetic instruments are often located in remote areas, and a public communication means is relatively backward or does not exist at all, which makes manual communication more difficult, and is not conducive to the performance of the above operation flow.